1. Technical Field
This invention relates generally to alternators, and more specifically to an improved alternator fan.
2. Description of the Related Art
Automotive alternators commonly use a rotor to provide a changing magnetic field within the machine. This is accomplished by rotating the rotor assembly within the stator core. A standard claw-pole rotor contains a north pole, a south pole, a wound field coil, shaft, slip rings, a front fan and a rear fan. These fans are attached to each end of the rotor assembly and supply the required cooling for the machine by forcing airflow there around.
It is well known that manipulating fan blade geometry, number of blades, and blade spacing can greatly influence airflow rate. One known type of alternator fan is a stamped component with cut-out fan blades. Further, portions of the fan blades are formed essentially by folded up sections of the component. In other words, the fan includes a center portion having blades extending from the center portion. A disadvantage of this type of alternator fan is that the fan blades vibrate and may ultimately break off. Therefore, they may not perform well under the increasingly demanding acceleration conditions of new alternators.
One known design feature used to increase the strength of these types of fan blades involves using gussets and other support structures. However, these design features result in an adverse effect. The disadvantages of manipulating fan blade geometry result in weakening the overall fan structure and increasing turbulence induced broadband noise within the vehicle.
From the above it can be seen that there exists a need for an improved alternator cooling fan. An object of this invention is to provide such an improved alternator fan.
The present invention addresses these drawbacks by providing a fan for a motor vehicle alternator, the fan being made from a generally disc-shaped body having opposed first and second faces and defining an axis of rotation centrally therethrough. Further, the body has a plurality of ribs defining raised peaks on the first face and recessed valleys on the second face.
There are numerous advantages of the alternator fan of the present invention. One advantage is an improved capacity to operate at high speeds with greater durability. A second advantage is the potential to increase the number of blades since the present invention does not require cut-outs to form the blades. A third advantage is decreased turbulence due to the ability to integrate a cusp into the body for increased airflow and smoother blade transitions. The decrease in turbulence reduces the induced broadband noise created during operation of the alternator. A fourth advantage is a larger surface area allowing for a continuous mounting surface and improved heat transfer. A fifth advantage is that if the component is stamped from metal, the piece of sheet metal can be thinner than what is required for known alternator fan designs.